Move frame_sink_id management to framesink_manager.cc/h from

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 92696ade86a16ef4b7811f318b7e6f13a05c43ab..3a498c9addf249b346233320c14878ee3c44fa24 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -45,6 +45,7 @@ class LayerTreeDebugState;
 class LayerTreeHost;
 class RendererSettings;
 class SurfaceManager;
+class FrameSinkManager;
 class TaskGraphRunner;
 }
 
@@ -101,6 +102,8 @@ class COMPOSITOR_EXPORT ContextFactoryPrivate {
   // Gets the surface manager.
   virtual cc::SurfaceManager* GetSurfaceManager() = 0;
 
+  virtual cc::FrameSinkManager* GetFrameSinkManager() = 0;
+
   // Inform the display corresponding to this compositor if it is visible. When
   // false it does not need to produce any frames. Visibility is reset for each
   // call to CreateCompositorFrameSink.